This invention relates to a method of completing a well that penetrates a subterranean formation and more particularly relates to a method of controlling the production of sand from an unconsolidated hydrocarbon-bearing formation.
Hydraulic fracturing techniques are commonly employed in the completion of wells to enhance the recovery of hydrocarbons from subterranean hydrocarbon-bearing formations. In carrying out such techniques, a fracturing fluid is injected down a well and into contact with the formation to be fractured. Hydraulic pressure is applied via the fracturing fluid to fracture the formation and thereafter fracturing fluid is injected into the formation propagate the fracture thereinto. Propping material is usually included in the fracturing fluid to prop the fracture that is formed. It is commonly accepted that at depths greater than about 2000 to 3000 feet most formations have preferred vertical fracture orientations and fractures formed therein by hydraulic fracturing techniques are vertically disposed fractures.
In U. S. Pat. No. 3,642,068 there is disclosed a fracturing process wherein a fracture is formed in a formation, is acid etched near the well, and is particle propped in the more remote portions of the fracture. In U. S. Pat. No. 3,687,203 there is described a process wherein a fracture is initiated in a non-productive zone and is extended vertically upward into a producing zone. Propping material is injected into the fracture and settles in the bottom portion thereof and fills the fracture to some height less than the height of the fracture to hold open a portion of the fracture above the settled material. This open portion allows the part of the fracture in the producing zone to have infinite ability to conduct production flow from the formation into the wellbore. In U. S. pat. No. 3,126,056 there is described a method of propping and sealing a fracture in a petroleumproducing formation for preventing substantially undesirable water flow with the petroleum produced therefrom. A vertical fracture is formed and the lower part of the fracture is sealed to block the portion of the formation that is expected to produce undesirable quantities of water but not to block the portion of the formation from which petroleum is to be produced.
Hydrocarbons are many times found in subterranean unconsolidated formations. Such formations are normally poorly cemented sandstone formations which may in some instances have little or no cementing material holding the sand grains together.
The production of hydrocarbons from unconsolidated formations may result in the production of sand from the formation along with the hydrocarbons. The production of sand is undesirable for many reasons. It is abrasive to components within the well such as tubing, pumps, and valves and may partially or completely clog the well.
Various techniques have been used for controlling the flow of sand from unconsolifated formations. Many of these techniques employ the use of slotted or screened liners or gravel packs to prevent the sand from being transported along with the hydrocarbons into the well. Other techniques make use of consolidating plastic material to cement the grains together and thereby prevent caving. Still other techniques include hydraulic fracturing techniques wherein the unconsolidated formation is fractured and propping material is deposited in the fracture. The propping material in the fracture may be consolidated to improve the stability of the propped fracture.
In U. S. Pat. No. 3,138,205 there is described a method for fracturing a subsurface formation with a fracturing fluid containing a propping agent and consolidating the propping agent in the fractures to maintain the fracture propping agents in place. In U.S. Pat. No. 3,343,600 there is described a technique for simultaneously fracturing and consolidating a relatively, loose, weak or semi-consolidated subterranean oil- or gas- containing formation. The formation is fractured by injecting a fracturing fluid into the formation under sufficient pressure to fracture the formation and the fracture is propagated by continuing to inject fracturing fluid into the formation. A dilute solution of a plastic or resinous consolidating agent is circulated into the formation via the fracture to consolidate the formation surrounding and defining the fracture. A propping agent may also be injected into the fracture and consolidated therein. Other techniques for fracturing and propping unconsolidated subterranean formations are described in U. S. Pats. Nos. 3,428,122 and 3,815,680.
As previously mentioned, gravel-packing techniques are commonly employed for controlling the production of sand from unconsolidated formations. Such a technique is described in U. S. Pat. No. 3,708,013. In accordance with this technique, materials are flowed through casing perforations to provide a consolidated gravel pack adjacent a subsurface formation. Thereafter, further perforations are formed through the casing to extend into and terminate within the consolidated gravel pack. It is noted that in such a gravel pack the horizontal thickness thereof may be a minimum near the upper perforations because of the tendency for the granulated material to settled away from the upper extension of the cavity about the casing into which the pack is formed. Therefore, a packer may be set in the casing to seal the upper perforations and eliminate flow through those perforations adjacent the portion of the gravel pack having the least horizontal thickness, thereby eliminating the possibility that unconsolidated sands from the formation will be produced through those upper perforations into the casing.
In U. S. Pat. No. 3,796,883 the effectiveness and competency of a well gravel pack and changes therein are determined by monitoring the location of radioactive pellets within the gravel pack. The effectiveness of formation fracturing and the location and orientation of such fractures have also been ascertained by the use of radioactive logs. Such reservoir engineering techniques are discussed in OIL RESERVOIR ENGINEERING by Silvain J. Pirson, 1958, at page 232, where it is said that another reservoir engineering use of tracer studies in a well is to ascertain the effectiveness of formation fracturing and the location and orientation of such fractures. For this purpose the radioactive tracer is plated on part of the propping sand and is used as the last batch injected with the fracturing fluid. The logging procedure is the same as for permeability-profiling determination: conventional log, base log, first run after completion of injection, and continued logging at intervals to ascertain wash out of plating material.